The present invention relates to a hydraulic clutch assembly, and more particularly to a hydraulic clutch assembly equipped with a spring-drive hydraulic clutch, which includes a gear rotatably mounted on a transmission shaft and a clutch cylinder fixedly mounted on the transmission shaft, first and second friction elements respectively supported on the gear and the clutch cylinder in such a manner as to be slidable along an axis of the clutch (hereinafter sometimes referred to a clutch axis) and relatively non-rotatable thereto, a pressure disk disposed opposite to the friction elements, and a spring for moving the pressure disk towards the friction elements to bring the first friction element into engagement with the second friction element, in which the pressure disk is moved away from the friction elements by an effect of hydraulic pressure, thereby withdrawing the friction elements from engagement with each other.
In a vehicle with a transmission equipped with the spring-drive hydraulic clutch, the hydraulic clutch is inevitably held in an engaged state when no hydraulic pressure is applied thereto. Accordingly, when an engine of the vehicle has been accidentally stopped, it can be restarted by a so-called pull-start by manually moving the vehicle.
In a vehicle equipped with both the spring-drive hydraulic clutch and a hydraulic-drive hydraulic clutch, it is enough to provide the transmission shaft with a single operational fluid passage for both the hydraulic clutches. As a result, a structure for feeding working fluid to both hydraulic clutches can be simplified.
The hydraulic clutch assembly of the above type having the spring-drive clutch is known for example in Japanese Patent Application Laid-open No. 2000-352446.
However, the spring-drive hydraulic clutch assembly of the conventional type as described in the above-cited publication poses problems as described below.
The spring-drive hydraulic clutch assembly of the conventional type includes a gear rotatably mounted on a transmission shaft, a clutch cylinder fixedly mounted on the transmission shaft, first and second friction elements respectively supported on the gear and the clutch cylinder in such a manner as to be slidable along the clutch axis and relatively non-rotatable thereto, a pressure disk disposed opposite to the friction elements, a spring for pressing the pressure disk towards the friction elements, a hydraulic piston for pressing the pressure disk away from the friction elements against biasing force of the spring upon receiving an effect of hydraulic pressure, and a hydraulic cylinder enclosing the hydraulic piston.
Specifically, the hydraulic cylinder is of an annular shape, which is integrally formed on the clutch cylinder and radially outwardly extending therefrom so as to cover the clutch cylinder. A radially outward portion of the pressure disk protrudes outwardly through the clutch cylinder, while the hydraulic piston is arranged so as to abut against the protrusion of the pressure disk. When the pressure disk is shifted away from the friction elements by the actuation of the hydraulic piston, the clutch is released from an engaged state.
Thus, the conventional spring-drive hydraulic clutch is disadvantageous in the fact that its clutch engagement release mechanism is of a complicated structure and the hydraulic cylinder is positioned on the radially outward side of the clutch cylinder, hence inviting increase in the entire size of the hydraulic cylinder.
It is an object of the present invention to provide a new hydraulic clutch assembly, which is of a relatively simple structure and includes a clutch engagement releasing mechanism that is capable of being placed substantially within an outer diameter of the clutch cylinder.
It is another object of the present invention to provide a new hydraulic clutch assembly that enables a hydraulic-drive clutch to be aligned with a spring-drive hydraulic clutch with a relatively simple structure.
It is still another object of the present invention to provide a clutch assembly that has an improved lubricant feeding structure for a spring-drive hydraulic clutch and a hydraulic-drive hydraulic clutch aligned therewith, aiming at effectively utilizing lubricant.
According to the present invention, there is provided a hydraulic clutch assembly equipped with a spring-drive hydraulic clutch, the hydraulic clutch including: a gear rotatably mounted on a transmission shaft and a clutch cylinder fixedly mounted on the transmission shaft; a first group of friction elements respectively and relatively non-rotatably supported on the gear and the clutch cylinder in such a manner as to be slidable along an axis of the clutch; a pressure disk disposed opposite to the first group of friction elements; a spring for moving the pressure disk towards the first group of friction elements to bring the friction elements into engagement with each other; a piston disposed in such a manner as to be slidable along the axis of the clutch on the opposite side of the pressure disk with the first group of friction elements therebetween, thereby forming a hydraulic fluid chamber within the clutch cylinder; an operation disk disposed in such a manner as to be slidable along the axis of the clutch between the piston and the first group of friction elements; and an interlocking rod extending along the axis of the clutch for interlocking the operation disk with the pressure disk in such a manner as not to be relatively movable with respect to each other. In this arrangement, the pressure disk is moved away from the first group of friction elements through the operation disk and the interlocking rod by an effect of hydraulic pressure acting on the piston, so that the friction elements are released from engagement with each other.
In the clutch assembly having the above arrangement, the clutch releasing mechanism of the spring-drive hydraulic clutch is constituted not by installing the hydraulic cylinder, which is integrally formed with the clutch cylinder, on the clutch cylinder, but by the operation disk, the piston and the interlocking rod, all of which can be placed within the outer diameter of the clutch cylinder. As a result of the omission of the hydraulic cylinder, a simplified structure can be achieved, and the outer diameter of the hydraulic clutch can be prevented from exceeding the outer diameter of the clutch cylinder, thereby achieving the reduced size of the hydraulic clutch assembly.
In a preferable aspect of the hydraulic clutch assembly, the clutch cylinder forms cutaway portions in an outer circumferential wall thereof, the cutaway portions extending along the axis of the clutch; the pressure disk and the operation disk respectively have protrusions which project into the cutaway portions of the clutch cylinder; and the interlocking rod interlocks the protrusion of the pressure disk with the protrusion of the operation disk.
According to the above arrangement, the interlocking between the operation disk and the pressure disk by means of the interlocking rod can be achieved in remarkably easy manner. Also, at least a part of the interlocking rod can be positioned in the cutaway portion. This enables the outer diameter of the entire hydraulic clutch to be efficiently reduced.
In a more preferable aspect, the protrusions are engaging protrusions to be fitted in the cutaway portions so as to enable the pressure disk and the operation disk to be relatively non-rotatable with respect to the clutch cylinder.
According to the above arrangement, with a simple construction, the operation disk and pressure disk can be securely brought into a non-rotatable state with respect to the clutch cylinder. As a result, engaging force effected by the hydraulic clutch can be increased.
In a more preferable aspect, the second friction element supported on the clutch cylinder has engagement protrusions formed on an outer circumference thereof and being respectively fitted into the cutaway portions so as to be relatively non-rotatable with respect to the clutch cylinder.
According to the above arrangement, it is possible to simplify the connecting structure between the clutch cylinder and the second friction element, which is supported on the clutch cylinder in such a manner as to be sidable along the axis of the clutch and relatively rotatable thereto.
That is, for example, by forming spline teeth on the inner circumference of the clutch cylinder and the outer circumference of the second friction element to be meshed with each other, it is possible to obtain the connection structure between the clutch cylinder and the second friction element. Although this spline teeth arrangement can achieve the connection structure, the above preferable aspect can achieve a simpler structure than this spline teeth arrangement.
In a still preferable aspect, the hydraulic clutch assembly further includes a hydraulic-drive hydraulic clutch. The hydraulic-drive hydraulic clutch includes: a second gear rotatably mounted on the transmission shaft so as to be positioned opposite to the gear with the clutch cylinder therebetween; a second group of friction elements, the first and second friction elements respectively supported on the second gear and the clutch cylinder in such a manner as to be sidable along the axis of the clutch and relatively non-rotatable thereto; a second piston disposed opposite to the piston with a partition wall therebetween, the partition wall formed in the clutch cylinder, the second piston being slidable along the axis of the clutch; and a second spring for biasing the second piston away from the second group of the friction elements. In this arrangement, the friction elements can be brought into an engaged state with each other by having hydraulic pressure acting on the second piston, and the transmission shaft forms a single operational fluid passage for feeding and discharging therethrough pressurized fluid to the hydraulic-drive hydraulic clutch and the spring-drive hydraulic clutch, respectively.
In a more preferable aspect, the single operational fluid passage is communicated with any one of hydraulic fluid chambers of the spring-drive hydraulic clutch and the hydraulic-drive hydraulic clutch; and the partition wall of the clutch cylinder forms therein a fluid passage hole for communication between both the hydraulic fluid chambers.
In a still more preferable aspect, the transmission shaft forms therein a single lubricant passage for feeding lubricant to the first group of friction elements in the spring-drive hydraulic clutch and the second group of friction elements of the hydraulic-drive hydraulic clutch, respectively. The piston and second piston respectively have inner circumferences, which form first and second hydraulic fluid passages for communication between the single lubricant passage and the inside of the clutch cylinder. The first and second hydraulic fluid passages respectively define openings communicated with the single lubricant passage. The openings is widened when the first and second pistons are shifted to positions respectively bringing the first group of friction elements into the engaged state, and the second group of friction elements into the engaged state.
According to the above arrangement, it is possible to feed a large amount of lubricant to the hydraulic clutch in the engaged state, while reducing the feeding rate of lubricant or feeding no lubricant to the hydraulic clutch in the disengaged state. As a result, the hydraulic pump can have a reduced volume and achieve reduced loss of the horsepower thereof.